1. Field of the Invention
The present invention relates to a technique for judging the tire width and tread of a vehicle and, more particularly, to a technique for judging the tire width and tread of a vehicle, in which a plurality of contact points are set in a treadle, lying across a road, and ON/OFF states of these contact points are scanned, to judge the tire width and tread of a vehicle, and then the detected tire width and the tread are provided as basic data for judging the kind of vehicle.
2. Description of the Related Art
A general highway toll collecting system is divided into a closed system which charges a toll according to the kind of a vehicle and the distance covered from an entrance tollgate to an exit tollgate, and an open system which charges a fixed toll depending on the kind of a vehicle passing through the tollgate. Unmanned toll collecting apparatuses are being introduced into these highway toll collecting systems, one of which is an apparatus for automatically judging the kind of vehicle, disclosed in Korean Patent Publication No. 86-2209 (Publication Date: Dec. 31, 1986).
In an earlier apparatus for automatically judging the kind of vehicle, a vehicle pass way corresponding to one lane through which vehicles pass is provided and vehicle separators are located opposite to each other and have the vehicle pass way therebetween. The vehicle separators have multiple pairs of light emitting devices and light receiving devices.
A treadle located across the vehicle pass way for measuring the tire width and tread of a vehicle includes resistance contact points. When the left and right tires of a passing vehicle tread on the contact points, the resistance value of the contact points changes and thus the tire width and tread can be measured based on the variation in the resistance value.
The treadle includes two contact point resistors, one located on the left side of the pass way and the other located on the right side of the pass way. The contact point resistors have narrow and long lower resistors and strip-shaped upper conductive resistors placed above the lower resistors by a predetermined distance therefrom. The treadle also includes a plurality of parallel contact points, their opening/closing patterns being used for judging the forward and backward motions of a vehicle passing through the pass way.
By measuring the various resistance values of the resistors, the tread and tire width of a vehicle passing through the pass way can be measured.
In an earlier apparatus for automatically judging the kind of vehicle, a treadle including contact point resistors as noted above is provided. Also provided is an interface circuit for converting the resistance value supplied from the treadle into a corresponding voltage and an A/D converter for converting the voltage from the interface circuit into corresponding digital data. Also provided is a memory circuit for storing a program for system operation and for temporarily storing data related to the tire width and treads of vehicles. Also provided is an interrupt controller for controlling the generation of an interrupt, and microprocessor for performing an operation for calculating the tire width and tread according to the system program stored in the memory, and main controller for finally judging the kind of vehicle according to digital data about the tire width and tread provided by the microprocessor and other various data and an interface circuit for interfacing the microprocessor with the main controller.
In the aforementioned method of judging the tire width and tread using the electrical resistance, the width of both tires and tread can not be measured without using the data from both contact point resistors.
However, when a vehicle passes through the pass way while driving all the way over towards one side thereof, both tires tread on only one of the contact point resistors and accordingly, data about one of the tires can not be obtained.
Furthermore, when the contact point resistors are short-circuited or open-circuited, errors are generated in the judgement of the tire width and tread.
In addition, it is impossible to individually manage a specific point of the contact point resistors.
Lastly, only after the treadle has been completely manufactured, can it be decided whether or not the treadle can be used and this increases a burden on its fabrication process.